It is previously known that only spermatozoa with a good ability to move and with a relatively straightlined progressive motility have the possibility to achieve fertilization and that only the spermatozoa with the best morphology enter the cervical mucus (Fredricsson B. and Bjork G. (1977): Morphology of postcoital spermatozoa in the cervical secretion and its clinical significance. Fertil. Steril. 28:841-845). It is also previously known that serum support sperm motility/Austin R. (1985) "Sperm maturation in the male and female genital tracts." In: Biology of Fertiliztion, vol. 2 (eds C Metz and A Monroy) pp. 121-147, Academic Press, New York/and is therefore used in connection with sperm separation for fertilization in vitro.
However, there are problems inherent in the use of a fluid comprising thousands of components and a specific active component would give a safer and more predictible effect than such a fluid. An active factor would also give the effect without dangerous concomittant actions e.g. immunologic factors or infectious diseases.